Warm-up apparatus for fuel cell

ABSTRACT

A warm-up apparatus GS for a fuel cell  1, 51  comprising: a compressor  22, 71  for feeding supply gas A to the fuel cell  1, 51 ; a main passage W 1 , W 3  connecting the compressor  22, 71  and the fuel cell  1, 51  and feeding supply gas A; an intercooler  23, 73  arranged in the main passage W 1 , W 3 ; and a bypass passage W 2 , W 4  connecting the compressor  22, 71  and the fuel cell  1, 51  and feeding supply gas A in such a manner that the supply gas A bypasses the intercooler  23, 73.

RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.10/117,362 which was filed on Apr. 5, 2002. The contents of theaforementioned applications are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a warm-up apparatus for a fuel cell.

BACKGROUND OF THE INVENTION

In recent years, fuel cells have been focused as a power plant ofelectric vehicles because of its cleanness and excellent energyefficiency. In the fuel cell, oxygen is fed to the cathode and hydrogenis fed to the anode, and electricity is generated with the reactionbetween hydrogen and oxygen. For the purpose of supplying oxygen to thecathode, for example, a compressor is used to feed oxygen-containing airto the fuel cell.

Upon feeding oxygen-containing air to the fuel cell, the temperature ofthe air is raised by the compressive force of the compressor. The fuelcell efficiently generates electricity at a particular temperature range(80 to 90° C. in the case of polymer electrolyte fuel cell). However,air compressed by the compressor rises, for example, to 120° C. If airhaving such a high temperature is fed to the fuel cell, effectivegeneration of electricity cannot be achieved. For this reason, air,before supplying to the fuel cell, passes through an intercooler and iscooled to a predetermined temperature, and thereafter the cooled air isfed to the fuel cell.

At the start of the fuel cell, the fuel cell is often cool, andeffective generation of electricity is not achieved. Therefore, the fuelcell has to be heated (warmed up) instantly to a certain desiredtemperature at the actuation of the fuel cell. This is particularlyimportant if the fuel cell is mounted on an electric vehicle.

In a conventional method, the fuel cell is heated by an electric heaterdriven by a battery or commercially available power source or by ahydrogen-combustion heater such as disclosed in U.S. Pat. No. 6,103,410.

However, in the conventional method, since the electric heater orhydrogen-combustion heater is employed only for the purpose of warmingup the fuel cell, consumption of electricity or hydrogen increases. Andif the fuel cell is mounted on an automobile, running distance per unitfuel consumption decreases. In an electric heater employing acommercially available power source, there is a drawback in thatelectricity has to be introduced from the outside. Furthermore, thewhole fuel cell system increases its size because there is a need toprovide a dedicated electric heater or hydrogen-combustion heater.

If air temperature is low in a cold area or in the wintertime, thetemperature of exhaust gas from the fuel cell is extremely low at thetime of start up. In this instance, consumption of electricity orhydrogen will increase seriously for warming up the fuel cell.Furthermore, moisture in the fuel cell may be frozen below freezingtemperature, which causes the fuel cell to generate little electricity.Therefore, it is necessary to warm up the fuel cell instantly.

In view of the above, a first object of the present invention is toprovide a warm-up apparatus for a fuel cell, which enables quickwarming-up of the fuel cell at the time of start up, and which does notrequire a dedicated electric heater or hydrogen-combustion heater.

Meanwhile, upon warming up the fuel cell, high-temperature air that iswarmed by the compressor may be fed directly to the fuel cell. Thisallows the fuel cell to be warmed up instantly by the high-temperatureair.

However, in a conventional method, high-temperature air is fed only tothe cathode of the fuel cell. Therefore, the anode of the fuel cell iswarmed up by heat that is transferred from the cathode through themembrane. For this reason, the anode is warmed up after the cathode,leading to a drawback that the whole fuel cell system takes time tocomplete a warm-up.

The anode of the fuel cell is also moisturized by an anode humidifier.Therefore, below freezing temperature, devices in the anode system aremost likely frozen. However, since high-temperature air is fed from thecompressor to the cathode of the fuel cell, warming-up is carried outmerely for the cathode humidifier, and the anode circulation device andthe anode humidifier are not warmed up at all.

In view of the above, a second object of the present invention is toprovide a warm-up apparatus for a fuel cell, which enables warming-up ofthe fuel cell not only for devices in the cathode system but for devicesin the anode system, and which enables warming-up for both the cathodeand the anode to thereby warm up the whole fuel cell system quickly.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provideda warm-up apparatus for a fuel cell comprising:

a compressor for feeding supply gas to the fuel cell;

a main passage connecting the compressor and the fuel cell and feedingsupply gas and;

an intercooler arranged in the main passage; and

a bypass passage connecting the compressor and the fuel cell and feedingsupply gas in such a manner that the supply gas bypasses theintercooler.

In this warm-up apparatus, upon feeding supply gas from the compressorto the fuel cell, supply gas is cooled at the intercooler if it flowsthrough the main passage, and the supply gas is not cooled if it flowsthrough the bypass passage bypassing the intercooler. Therefore, duringthe normal driving which requires cooling supply gas, supply gas is fedthrough the main passage. On the other hand, at the start up of the fuelcell which requires a warming-up, supply gas is fed through the bypasspassage to raise the temperature thereof and a warm supply gas is fed tothe fuel cell. According to this warm-up apparatus, a warm supply gas isfed to the fuel cell at the time of start up. This enables quickwarming-up of the fuel cell without requiring a dedicated electricheater or hydrogen-combustion heater.

In the aforementioned warm-up apparatus, a cross-sectional area of thebypass passage may be smaller than that of the main passage.

In this warm-up apparatus, the cross-sectional are of the bypass passageis set smaller than that of the main passage. Elevation in temperatureof supply gas from the compressor is determined in accordance with thecompression ratio of the compressor. The smaller the cross-sectionalarea of the passage into which supply gas from the compressor flows, themore does the compression ratio of the supply gas increase whensupplying supply gas having the same flow rate. Temperature of supplygas increases as the compression ratio increases. For this reason, thecross-sectional area of the bypass passage into which supply gas flowsat the time of warming-up is set smaller than that of the main passagefor feeding supply gas during the normal operation, so that supply gasat a high temperature is fed to the fuel cell. Therefore, it is possibleto warm up the fuel cell quickly.

In the aforementioned warm-up apparatus, supply gas may be fed either tothe main passage or the bypass passage in accordance with a warming-upstate of the fuel cell.

In this warm-up apparatus, supply gas is fed either to the main passageor the bypass passage in accordance with a warming-up state of the fuelcell. When the fuel cell is not warmed up yet, supply gas that is warmedand raised the temperature by the compressor is fed to the fuel cell.When the fuel cell is warmed up, supply gas is fed through the mainpassage. Supply gas having an elevated temperature is cooled at theintercooler and then fed to the fuel cell.

In the aforementioned warm-up apparatus, a flow rate adjustment devicemay be provided for adjusting a ratio of flow rates of supply gas, whichpasses through the main passage and the bypass passage.

In this warm-up apparatus, of the flows of supply gas toward the fuelcell, the flow rate of supply gas to be fed to the main passage and theflow rate of supply gas to be fed to the bypass passage are adjusted.When a warm-up of the fuel cell is not ready and the fuel cell is cool,all supply gas is fed to the bypass passage so that the temperature ofsupply gas is raised to warm up the fuel cell. Thereafter, when the fuelcell becomes warmer, a flow of supply gas is switched gradually from thebypass passage to the main passage. Accordingly, it is possible to feedsupply gas having an appropriate temperature to the fuel cell until awarm-up of the fuel cell is completed from a state where the fuel cellis cool.

In the aforementioned warm-up apparatus, a flow rate of supply gasflowing through the bypass passage may be adjusted in accordance with awarming-up state of the fuel cell.

In this warm-up apparatus, of the flows of supply gas toward the fuelcell, a flow rate of supply gas flowing through the bypass passage isadjusted in accordance with a warming-up state of the fuel cell.Accordingly, if a load of the fuel cell decreases during the drive ofthe fuel cell, and if the fuel cell requires a warm-up, in accordancewith a state of the fuel cell, the flow rate of supply gas flowingthrough the bypass passage is adjusted. Therefore, although during thedrive of the fuel cell, quick warming-up of the fuel cell is achieved.

In the aforementioned warm-up apparatus, the number of revolutions ofthe compressor may be controlled in accordance with a warming-up stateof the fuel cell.

In this warm-up apparatus, the number of revolutions of the compressoris controlled in accordance with a warming-up state of the fuel cell.For example, by way of controlling the number of revolutions of thecompressor when the temperature of supply gas at the input side of thefuel cell is elevated to a high temperature, such as 80° C. or more, thetemperature of supply gas flowing toward the fuel cell is decreased.Accordingly, it is possible to supply to the fuel cell supply gas havinga temperature suitable for generation of electricity.

According to a second aspect of the present invention, there is provideda warm-up apparatus for a fuel cell comprising:

an air supply section for feeding air to a cathode of the fuel cell, theair supply section including a compressor for compressing and conveyingair, and an air passage connecting the compressor and the cathode of thefuel cell; and

a hydrogen supply section for feeding hydrogen to an anode of the fuelcell, the hydrogen supply section including a hydrogen passageconnecting a hydrogen supply source and the anode of the fuel cell;

wherein the air passage includes a main passage and a bypass passage,the main passage being provided with an intercooler for cooling airflowing from the compressor to the fuel cell and the bypass passagebypassing the intercooler; and

wherein a heat exchanger is arranged between the air passage and thehydrogen passage so as to transfer the heat of air to hydrogen.

In this warm-up apparatus, the air passage includes the main passage, inwhich an intercooler is provided for cooling air flowing from thecompressor to the cathode of the fuel cell, and the bypass passagebypassing the intercooler. Upon feeding supply gas from the compressorto the fuel cell, supply gas is cooled at the intercooler if it flowsthrough the main passage, and the supply gas is not cooled if it flowsthrough the bypass passage bypassing the intercooler. Therefore, duringthe normal driving which requires cooling supply gas, supply gas is fedthrough the main passage. On the other hand, at the start up of the fuelcell which requires a warming-up, supply gas is fed through the bypasspassage to raise the temperature thereof and a warm supply gas is fed tothe fuel cell. According to this warm-up apparatus, a warm supply gas isfed to the fuel cell at the time of start up. This enables quickwarming-up of the fuel cell without requiring a dedicated electricheater or hydrogen-combustion heater.

Furthermore, a heat exchanger is arranged between the air passagethrough which air is fed to the cathode of the fuel cell and thehydrogen passage through which hydrogen is fed to the anode of the fuelcell so that the heat of air transfers to hydrogen. Air flowing throughthe air passage is raised its temperature by adiabatic compression ofthe compressor. For this reason, the heat of air will be transferred tohydrogen via the heat exchanger so as to raise the temperature ofhydrogen. Therefore, it is not necessary to provide a dedicated electricheater or hydrogen-combustion heater. By way of raising the temperatureof hydrogen, not only devices in the cathode system but for devices inthe anode system are warmed up, and the cathode and anode of the fuelcell are quickly warmed up, thereby completing warming-up of the wholefuel cell system quickly.

In the aforementioned warm-up apparatus, a heat quantity adjustmentdevice may be employed for adjusting a heat quantity of air flowing tothe fuel cell in such a manner that a supply of air is switched betweenthe main passage and the bypass passage.

In this warm-up apparatus, a heat quantity adjustment device is employedfor adjusting a heat quantity of air flowing to the fuel cell in such amanner that a supply of air is switched between the main passage and thebypass passage. Accordingly, air and hydrogen each having an appropriatetemperature will be fed to the fuel cell.

According to a third aspect of the present invention, there is provideda warm-up apparatus for a fuel cell comprising:

an air supply section for feeding air to a cathode of the fuel cell, theair supply section including a compressor for compressing and conveyingair, and an air passage connecting the compressor and the cathode of thefuel cell; and

a hydrogen supply section for feeding hydrogen to an anode of the fuelcell, the hydrogen supply section including a hydrogen passageconnecting a hydrogen supply source and the anode of the fuel cell;

wherein a heat exchanger is arranged between the air passage and thehydrogen passage so as to transfer the heat of air to hydrogen.

In this warm-up apparatus, a heat exchanger is arranged between the airpassage through which air is fed to the cathode of the fuel cell and thehydrogen passage through which hydrogen is fed to the anode of the fuelcell so that the heat of air transfers to hydrogen. An air flowingthrough the air passage is raised its temperature by adiabaticcompression of the compressor. For this reason, heat of the air will betransferred to hydrogen via the heat exchanger so as to raise thetemperature of hydrogen. Therefore, it is not necessary to provide adedicated electric heater or hydrogen-combustion heater. By way ofraising the temperature of the hydrogen, not only devices in the cathodesystem but for devices in the anode system are warmed up, and thecathode and anode of the fuel cell are quickly warmed up, therebycompleting warming-up of the whole fuel cell system quickly.

In the aforementioned warm-up apparatus, the air passage may include amain passage, in which an intercooler for cooling air is provided, and abypass passage, and a heat quantity adjustment device may be employedfor adjusting a heat quantity of air flowing to the fuel cell in such amanner that a supply of air is switched between the main passage and thebypass passage.

In this warm-up apparatus, the air passage includes a main passage, inwhich an intercooler is provided, and a bypass passage bypassing theintercooler. And a heat quantity adjustment device is employed foradjusting a heat quantity of air flowing to the fuel cell in such amanner that a supply of air is switched between the main passage and thebypass passage. Accordingly, air and hydrogen each having an appropriatetemperature will be fed to the fuel cell.

In the aforementioned warm-up apparatus according to the second and thethird aspect of the invention, a controller may be provided forcontrolling the heat quantity adjustment device in accordance with awarming-up state of the fuel cell.

In this warm-up apparatus, a controller controls the heat quantityadjustment device in accordance with a warming-up state of the fuel cellsuch that the heat quantity adjustment device switches the supply of airbetween the main passage and the bypass passage for controlling the heatquantity of air flowing to the fuel cell. Accordingly, air and hydrogeneach having an appropriate temperature will be fed to the fuel cell inaccordance with a warm-up state of the fuel cell. A warm-up state of thefuel cell can be determined, for example, by the temperature of exhaustair discharged from the fuel cell.

In the aforementioned warm-up apparatus according to the second and thethird aspect of the invention, a controller may be provided forcontrolling the heat quantity adjustment device in accordance withambient temperature.

Upon raising the temperature of air to a suitable temperature, more heatquantity is required if ambient temperature is lower. On the contrary,less heat quantity is required if ambient temperature is higher. In thiswarm-up apparatus, the heat quantity adjustment device is controlled inaccordance with ambient temperature. To be more specific, the flow rateof air flowing through the bypass passage is increased when ambienttemperature is low, and the flow rate of air flowing through the mainpassage is increased when ambient temperature is high. Accordingly, itis possible to feed air having an appropriate temperature.

In the aforementioned warm-up apparatus according to the second and thethird aspect of the invention, a controller may be provided forcontrolling the heat quantity adjustment device in accordance with ageneration of electricity at the fuel cell.

Since the amount of hydrogen consumption increases as a generation ofelectricity increases, it is preferable to increase or decrease the heatquantity of air in accordance with increment or decrement of theconsumption amount of hydrogen. For this reason, in this warm-upapparatus, the heat quantity adjustment device is controlled inaccordance with a generation of electricity at the fuel cell. To be morespecific, since the amount of hydrogen consumption is greater if theamount of electricity generation of the fuel cell increases, in order toprovide such a lot of hydrogen with heat, the heat quantity of air isincreased by way of increasing the flow rate of air flowing through thebypass passage. On the contrary, since the amount of hydrogenconsumption is smaller if the amount of electricity generation of thefuel cell decreases, such a small quantity of hydrogen requires lessheat. Therefore, the amount of air flowing through the main passage isincreased because a small quantity of heat is required for air.Accordingly, air and hydrogen each having an appropriate temperaturewill be fed to the fuel cell.

In the aforementioned warm-up apparatus according to the second and thethird aspect of the invention, a restriction may be provided in thebypass passage so that a degree of opening of the bypass passage isadjustable.

In this warm-up apparatus, a restriction is provided in the bypasspassage for adjusting a degree of opening of the bypass passage so thatthe diameter of the bypass passage is reduced or extended. Extending thediameter of the bypass passage enables the pressure of the compressor atthe output side to be enhanced. Therefore, the temperature of air iscontrolled by the diameter of the bypass passage. Accordingly, it ispossible to control air and hydrogen to have an appropriate temperatureby adjusting the diameter of the bypass passage.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention will be described below,by way of example only, with reference to the accompanying drawings, inwhich:

FIG. 1 is the overall arrangement of a fuel cell system including awarm-up apparatus for the fuel cell according to a first embodiment ofthe invention;

FIG. 2 is a schematic explanatory view illustrating the structure of thefuel cell shown in FIG. 1;

FIG. 3 is a flow chart showing a series of control flows of the warm-upapparatus according to the first embodiment from a start up to a warm-upmode;

FIG. 4 is a flow chart showing a series of control flows of the warm-upapparatus according to the first embodiment from the warm-up mode to asteady driving mode;

FIG. 5A is a map of temperature and airflow rate showing the relationsbetween the number of revolutions of a compressor and temperature ofsupply air, and FIG. 5B is a map of airflow rate and opening degree of apressure control valve showing the number of revolutions of thecompressor and opening degree of the pressure control valve;

FIG. 6 is the overall arrangement of a fuel cell system including awarm-up apparatus for the fuel cell according to a first modification;

FIG. 7 is a flow chart showing a series of control flows of the warm-upapparatus according to the first modification from the warm-up mode tothe steady driving mode;

FIG. 8 is the overall arrangement of a fuel cell system including awarm-up apparatus for the fuel cell according to a second modification;

FIG. 9 is the overall arrangement of a fuel cell system including awarm-up apparatus for the fuel cell according to a third modification;

FIG. 10 is the overall arrangement of a fuel cell system including awarm-up apparatus for the fuel cell according to a fourth modification;

FIG. 11 is the overall arrangement of a fuel cell system including awarm-up apparatus for the fuel cell according to a second embodiment ofthe present invention;

FIG. 12 is a schematic explanatory view illustrating the structure ofthe fuel cell shown in FIG. 11;

FIG. 13 is a flow chart partly showing a series of control flows of thewarm-up apparatus according to the second embodiment;

FIG. 14 is a flow chart showing other part of a series of control flowsof the warm-up apparatus according to the second embodiment;

FIG. 15 is a flow chart showing the rest of a series of control flows ofthe warm-up apparatus according to the second embodiment;

FIG. 16A is a flow chart showing a warm-up operation in the normal mode,and FIG. 16B is a graph showing the relations between temperature ofsupply air at a cathode humidifier and opening degree of a restrictionvalve;

FIG. 17 is the overall arrangement of a fuel cell system including awarm-up apparatus for the fuel cell according to a modification of thesecond embodiment; and

FIG. 18 is a sectional view of a common piping.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to first and second embodiments and their modifications of theinvention shown in the drawings, a warm-up apparatus for a fuel cellaccording to the present invention will be described.

First Embodiment

A warm-up apparatus for a fuel cell according to a fist embodiment ofthe invention will be described.

As referential figures relative to the fist embodiment, FIG. 1 is theoverall arrangement of a fuel cell system including the warm-upapparatus for the fuel cell according to the first embodiment, and FIG.2 is a schematic explanatory view illustrating the structure of the fuelcell shown in FIG. 1.

As shown in FIG. 1, the fuel cell system FCS comprises a fuel cell 1, anair supply section 2, a hydrogen supply section 3, a controller 4, etc.The fuel cell system FCS is an electricity generating system including afuel cell 1 as a primary construction. The warm-up apparatus GS (GS1)for the fuel cell 1 substantially consists of the air supply section 2and the controller 4. The fuel cell system FCS is mounted on anautomobile (fuel cell-mounted electric vehicle).

As shown in FIG. 2, the fuel cell 1 is divided into the cathode (oxygenpole) and the anode (hydrogen pole) across an electrolyte membrane 1 c,and each of the poles has an electrode containing a platinum seriescatalyst to form a cathode pole 1 b and an anode pole 1 d. As anelectrolyte membrane 1 c which can be used herein, a solidmacromolecular membrane, such as perfluorocarbon sulfonic acid, which isa proton-exchange membrane, has been known. The electrolyte membrane 1 chas a plurality of proton-exchanging groups in the solid macromolecule,and has a low specific resistance, when being saturated with water,lower than 20 Ω-proton at a normal temperature, thereby serving as aproton-conductive electrolyte.

Provided at the outside of the cathode pole 1 b is a cathode-side gaspassage 1 a for feeding supply air A as oxidant gas toward the cathodepole 1 b, and an anode-side gas passage 1 e is provided at the outsideof the anode pole 1 d for feeding supply hydrogen H as fuel gas towardthe anode pole 1 d. The inlet and outlet of the cathode-side gas passage1 a are connected to the air supply section 2, and the inlet and outletof the anode-side gas passage 1 e are connected to the hydrogen supplysection 3. Although the fuel cell 1 shown in FIG. 2 is illustrated as asingle cell for the purpose of simplifying the configuration, the fuelcell 1 is actually configured as a laminate structure havingapproximately 200 single cells laminated. Since the fuel cell 1generates heat by the electrochemical reaction when generatingelectricity, a non-shown cooling device is employed for cooling the fuelcell 1.

In the fuel cell 1, supply air A is fed through the cathode-side gaspassage 1 a and supply hydrogen H is fed through the anode-side gaspassage 1 d such that the protons produced at the anode pole 1 d by theionization of hydrogen in the presence of the catalyst are migrated inthe electrolyte membrane 1 c and reach the cathode pole 1 b. The protonsreaching to the cathode pole 1 b react with the oxygen ions producedfrom oxygen of the supply air A, thereby producing water. The producedwater and supply air A containing unused oxygen is discharged asdischarged air Ae from the outlet of the cathode of the fuel cell 1. Thedischarged air Ae contains a lot of moisture. At the time of ionizationof hydrogen, electrons e⁻ are produced in the anode pole 1 d. Theproduced electrons e⁻ reach the cathode pole 1 b via an external load Msuch as a motor.

As best seen in FIG. 1, the air supply section 2, which forms a part ofthe warm-up apparatus GS1, comprises an air cleaner 21, a compressor 22,an intercooler 23, a humidifier 24, a passage ON/OFF valve 25, a checkvalve 26, and a pressure control valve 27. Of these elements, theintercooler 23 is arranged in a main passage W1 extending between thecompressor 22 and the fuel cell 1. The passage ON/OFF valve 25 isarranged in the main passage W1 at the downstream of the intercooler 23.

A bypass passage W2 extends between the compressor 22 and the fuel cell1 in such a manner as to bypass the intercooler 23. Specifically, thebypass passage W2 branches from the main passage W1 at an intermediatebetween the compressor 22 and the intercooler 23, and joins the mainpassage W1 at an intermediate between the passage ON/OFF valve 25 andthe humidifier 24. Therefore, supply gas flowing through the bypasspassage W2 does not flow into the intercooler 23.

The cross-sectional area of the bypass passage W2 is smaller than thatof the main passage W1, and is set, for example, ½ or less with regardto the main passage W1. Because of the smaller cross-sectional area ofthe bypass passage W2, pressure of supply air A at the discharge side ofthe compressor 22 becomes higher when flowing through the bypass passageW2 than when flowing through the main passage W1. As a result, thecompression amount of the compressor 22 increases, leading to increasingtemperature of supply air A.

The air supply section 2 is provided with temperature sensors T1, T2,and T3 for detecting temperatures of supply air, discharged air, coolingwater, etc.

The air cleaner 21 consists of a non-shown filter and the like. The aircleaner 21 filters air (supply air) to be fed to the cathode of the fuelcell 1 to remove impurities or contaminants contained in the supply airA.

The compressor 22 mainly consists of a supercharger (not shown) and amotor (not shown) for driving the supercharger. The compressor 22applies adiabatic compression to supply air A that is used in the fuelcell as oxidant gas, and feeds the compressed air under pressure towardthe fuel cell 1. During adiabatic compression, supply air A is heated.The heated supply air A contributes to warming-up of the fuel cell 1.

The intercooler 23 is furnished with a cooling water channel, throughwhich cooling water flows. During the normal driving of the fuel cell 1,the intercooler 23 cools supply air from the compressor 22 by heatexchange between cooling water and supply air. The temperature of supplyair that is fed from the compressor 22 during the normal driving of thefuel cell 1 is usually about 120° C. However, the fuel cell 1 is drivenin the temperature range of about 80 to 90° C. For this reason, supplyair A is cooled down to a temperature of about 60 to 75° C., and thenintroduced into the fuel cell 1.

The humidifier 24 is a fuel cell discharged gas supplying type, andsubstantially consists of a housing and a bundle of hollow fibermembranes made by a number of, for example, 5000 hollow fiber membranesbound together and accommodated in the housing. Supply air A flowswithin the hollow fiber membranes, and discharged air Ae flows outsidethe hollow fiber membranes within the housing. Since water is producedin the fuel cell 1 upon generation of electricity and discharged air Aecontains a lot of water or moisture, supply air A is humidified bymoisture exchanging with the water. As the humidifier 24, any knowndevice may be used other than this fuel cell discharged gas supplyingtype. For example, one known humidifier (a kind of carburetor) comprisesa venturi, a water tank, a siphon tube connecting the venturi and thewater tank, etc, and supply air A is humidified by water, which isstored in the water tank for the purpose of humidifying air A and isdrawn by Venturi effect for spraying the same.

The passage ON/OFF valve 25 positions in the main passage W1 so thatsupply air A flows into the main passage W1 if the passage ON/OFF valve25 is ON and supply air A flows into the bypass passage W2 if thepassage ON/OFF valve 25 is OFF.

The check valve 26 positions in the bypass passage W2 to prevent acounter flow of supply air A.

The pressure control valve 27 consists of a butterfly valve (not shown),a stepping motor (not shown) for driving the butterfly valve, etc. Thepressure control valve 27 controls pressure (discharge pressure) ofdischarged air Ae that is discharged from the fuel cell 1 by decreasingor increasing the opening degree of the pressure control valve 27.Decreasing the opening degree of the pressure control valve 27 allowsthe fuel cell 1 to increase its discharge pressure, and therefore, thetemperature rising range of discharged air Ae increases proportionallyto the increasing discharge pressure. Meanwhile, increasing the openingdegree of the pressure control valve 27 allows the fuel cell 1 todecrease its discharge pressure, and therefore, the temperature risingrange of discharged air Ae decreases proportionally to the decreasingdischarge pressure.

The temperature sensor T1 comprises a thermistor and the like. Thetemperature sensor T1 detects temperature of supply air A at the inletof the cathode of the fuel cell 1, and transmits a detection signal tothe controller 4.

Likewise the temperature sensor T1, the temperature sensor T2 comprisesa thermistor and the like. The temperature sensor T2 detects temperatureof discharged air Ae at the outlet of the cathode of the fuel cell 1,and transmits a detection signal to the controller 4.

Likewise the temperature sensors T1, T2, the temperature sensor T3comprises a thermistor and the like. The temperature sensor T3 detectswater temperature of cooling water within the intercooler 23, andtransmits a detection signal to the controller 4.

As best seen in FIG. 1, the hydrogen supply section 3 comprises ahydrogen gas cylinder 31, a regulator 32, a hydrogen circulating pump33, etc.

The hydrogen gas cylinder 31 consists of a non-shown high-pressurehydrogen bomb, and stores supply hydrogen H to be introduced to theanode of the fuel cell 1. Stored supply hydrogen H is pure hydrogen, andthe pressure thereof ranges from 15 to 20 MpaG (150-200 kg/cm²G). Thehydrogen gas cylinder 31 may be made from hydrogen absorbing alloys, andmay store hydrogen at a pressure of about 1 MPaG (10 kg/cm²G).

The regulator 32 comprises a diaphragm (not shown), a pressureregulating spring (not shown) and the like. The regulator 32 is apressure control valve for decreasing pressure of supply hydrogen H thatis stored at a high pressure to a predetermined pressure so as to enablethe use of supply hydrogen H under a certain constant pressure.

The hydrogen circulating pump 33 comprises a non-shown ejector and thelike. The hydrogen circulating pump 33 utilizes a flow of supplyhydrogen H flowing toward the anode of the fuel cell 1 so as to absorbspent supply hydrogen H after the use in the fuel cell 1 as fuel gas,viz. discharged hydrogen He discharged from the anode of the fuel cell1, and circulates the spent supply hydrogen H. The reason forcirculating and utilizing discharged hydrogen is that supply hydrogen Hstored in the hydrogen gas cylinder 3 is pure hydrogen 1.

The controller 4, which forms a part of the warm-up apparatus GS1,although not shown, comprises a CPU, a memory, an input/outputinterface, an A/D converter, a bus, etc. The controller 4 entirely andsystematically controls the fuel cell system FCS as well as controlstemperature of supply air A to be fed to the fuel cell 1. As mentionedabove, the controller 4 receives detection signals from the temperaturesensors T1, T2, and T3. The controller 4 also transmits control signalswith respect to the compressor 22, the passage ON/OFF valve 25, thecheck valve 26, and the pressure control valve 27.

With reference to FIGS. 3 and 4, one operation example at star up of thewarm-up apparatus GS1 according to the first embodiment will bedescribed (see also FIG. 1 when necessary).

Herein, FIGS. 3 and 4 are flow charts showing a series of control flowsof the warm-up apparatus according to the first embodiment. In the flowshown in FIG. 4, heating amount of supply air A is controlled with thenumber of revolutions of the compressor 22. The target temperature ofsupply air A to be fed to the fuel cell 1 is in the range of between 65°C. and 80° C.

In FIG. 3, when the ignition switch of the fuel cell-mounted electricvehicle is ON (S1) for starting the electric vehicle, a predeterminedsystem check is carried out to determine whether a failure is detectedfor each device (S2). If a failure is detected in step S2, the operationproceeds to a predetermined failure treatment mode (S3) associating witheach failure state. Meanwhile, if no failure is detected in step S2, thenumber of revolutions of the compressor 22 is set (S4) such that theoptimum amount of supply air A is fed during idling. Subsequently, thetemperature of discharged air Ae at the output of the fuel cell 1 isdetected with the temperature sensor T2, and a detection is made as towhether the temperature Te2 of discharged air Ae is equal to or lowerthan 20° C. (S5). Since the temperature Te2 of discharged air Ae isdetected just after the air is discharged from the fuel cell 1, awarm-up state of the fuel cell 1 is determined depending on thetemperature of discharged air Ae.

As the result, if the temperature Te2 of discharged air Ae is higherthan 2020 C., it is determined that the warm-up has been completed, andthe operation proceeds to a steady electricity generation mode (S6). Ifthe temperature Te2 of discharged air Ae is equal to or lower than 20°C., it is determined that the fuel cell 1 has not been ready yet andrequires a warm-up. The operation then proceeds to a warm-up mode (S7).

With reference to FIG. 4, control after proceeding to the warm-up modewill be described. When the operation proceeds to the warm-up mode(S10), the water temperature of cooling water at the intercooler 23 isdetected with the temperature sensor T3, and a detection is made as towhether the water temperature Te3 of the cooling water is equal to orlower than 30° C. (S11). Herein, if the water temperature Te3 of thecooling water is higher than 30° C., it is determined that the fuel cell1 has been warmed up, and then the operation proceeds to the steadyelectricity generation mode (S12). Meanwhile, if the water temperatureTe3 of the cooling water is equal to or lower than 30° C., it isdetermined that the fuel cell has not been ready. yet and requires awarm-up. Therefore, supply air A from the compressor 22 is fed into thebypass passage W2 by closing the passage ON/OFF valve 25 (S13). Sincethe bypass passage W2 bypasses the intercooler 23, supply air A flowingthrough the bypass passage W2 is not cooled by the intercooler 23.Furthermore, the cross-sectional area of the bypass passage W2 issmaller than that of the main passage W1, and is set, for example, about½ with regard to the main passage W1. For this reason, when supply air Aflows into the bypass passage W2, pressure of the outlet of thecompressor 22 becomes greater than when supply air A flows into the mainpassage W1. As the result, compression amount of the compressor 22increases, allowing temperature of supply air A to rise further.Accordingly, a warm-up state of the fuel cell 1 is determined on thebasis of the water temperature of cooling water at the compressor 22 soas to feed supply air A either to the main passage W1 or to the bypasspassage W2 depending on the warm-up state of the fuel cell 1.

Supply air A, the temperature of which has risen after flowing throughthe bypass passage W2, is fed to the fuel cell 1 via the humidifier 24.Since high-temperature supply air A is fed to the fuel cell 1, it ispossible to complete a warm-up quickly.

After the passage ON/OFF valve 25 is closed, the temperature sensor T2checks the temperature of discharged air Ae at the output of the fuelcell 1 (S14). When the temperature of discharged air Ae is detected atthe output of the fuel cell 1, the number of revolutions of thecompressor 22 is detected from the map of temperature and air flow rateshown in FIG. 5A on the basis of the corresponding temperature of thedischarged air Ae. The number of revolutions of the compressor 22 is setto the detected value (S15). Subsequently, the opening degree of thepressure control valve 27 that is positioned at the output of the fuelcell 1 is set (S16). In this instance, with reference to the map of airflow rate and opening degree of the pressure control valve shown in FIG.5B, the opening degree of the pressure control valve 27 is set on thebasis of the number of revolutions of the compressor 22 such that thepressure of supply air A at the input of the fuel cell 1 is set to apredetermined value.

After the opening degree of the pressure control valve 27 is set, thetemperature sensor T1 checks the temperature Te1 of supply air A at theinput of the fuel cell 1 (S17). When the temperature Te1 of supply air Ais detected at the input of the fuel cell 1, a detection is made as towhether the temperature Te1 is higher than 80° C. (S18). The temperatureTe1 over 80° C. is sufficient for warming up the fuel cell 1. Therefore,if the temperature Te1 is higher than 80° C., the number of revolutionsof the compressor 22, and hence the compression amount of supply air A,is decreased so as to decrease the temperature of supply air A flowingto the fuel cell 1 (S19). Meanwhile, if the temperature Te1 is equal toor lower than 80° C., the compressor 22 goes on to drive without varyingthe number of revolutions of the compressor 22. Subsequently, thetemperature Te2 of discharged air Ae is detected at the output of thefuel cell 1 to determine whether the temperature Te2 is higher than 20°C. (S20). As the result, if the temperature Te2 is equal to or lowerthan 20° C., it is determined that the fuel cell 1 further requires awarm-up, and the operation returns to step S16 to control continuouslythe warm-up of the fuel cell 1. Meanwhile, if the temperature Te2 ishigher than 20° C., the passage ON/OFF valve 25 opens (S21). Supply airA from the compressor 22 is then fed to the main passage W1. Supply airA is fed through the main passage W1 to the fuel cell 1, therebycompleting the warm-up mode and shifting to the steady driving (S22).

As mentioned above, since supply air A is fed to the fuel cell 1 throughthe bypass passage W2 during a warm-up of the fuel cell 1, warm supplyair A bypassing the intercooler 23 is fed to the fuel cell 1.Furthermore, since the fuel cell 1 is warmed up quickly, there is noneed to provide a dedicated electric heater or hydrogen-combustionheater for warming up the fuel cell 1 at the start up. Furthermore,since supply air A flows into the intercooler 23 after completing thewarm-up of the fuel cell 1 and during the normal mode, it is possible tocontrol supply air A flowing to the fuel cell 1 such that thetemperature thereof would not rise too much.

In the first embodiment, the warm-up state is determined on the basis ofthe temperature Te2 of discharged air Ae that is discharged from thefuel cell 1 and the water temperature Te3 of cooling water at theintercooler 23. However, the warm-up state of the fuel cell 1 may bedetermined on the basis of either one of the temperatures Te2 and Te3.In this instance, of course the temperature sensor which is not used fordetermining the warm-up state of the fuel cell 1 may be omitted.

First Modification

A first modification of the warm-up apparatus for the fuel cell will bedescribed. Parts or elements similar to those previously describedregarding the first embodiment will be denoted by the same referencenumerals and the description thereof will be omitted.

Herein, FIG. 6 is the overall arrangement of a fuel cell systemincluding a warm-up apparatus for the fuel cell according to the firstmodification.

As shown in FIG. 6, the warm-up apparatus GS2 according to the firstmodification has substantially the same configuration as the warm-upapparatus GS1 according to the first embodiment. However, the warm-upapparatus GS2 includes a flow control valve 41 in place of the passageON/OFF valve 25 shown in FIG. 1. With such a configuration of thewarm-up apparatus GS2, it is possible to carry out a warm-up of the fuelcell 1 not only at start up but also during a low load operation otherthan start up.

With reference to FIG. 7, one operation example of the warm-up apparatusGS2 during the drive of the fuel cell 1 will be described (see also FIG.6 when necessary).

Herein, FIG. 7 is a flow chart showing a series of control flows of thewarm-up apparatus according to the first modification from the warm-upmode to the steady driving mode. In the flow shown in FIG. 7, heatingamount of supply air A is controlled with the opening degree of the flowcontrol valve 41.

In FIG. 7, when the operation of the fuel cell 1 proceeds to the warm-upmode (S30), the water temperature Te3 of cooling water at theintercooler 23 is detected with the temperature sensor T3, and adetection is made as to whether the water temperature Te3 is equal to orlower than 30° C. (S31). Herein, if the water temperature Te3 is higherthan 30° C., it is determined that the fuel cell does not require awarm-up, and then the operation proceeds to the steady driving (S32).Meanwhile, if the water temperature Te3 is equal to or lower than 30°C., it is determined that the fuel cell is still cold and requires awarm-up. In this event, the flow control valve 41 is closed (S33) suchthat supply air A from the compressor 22 flows through the bypasspassage W2. Subsequently, the temperature sensor T2 checks thetemperature Te2 of discharged air Ae at the output of the fuel cell 1(S34). When the temperature Te2 is detected, the number of revolutionsof the compressor 22 is set to a predetermined value (S35). The numberof revolutions of the compressor 22 is set, for example, to 3000 rpm.After setting the number of revolutions of the compressor 22, withreference to the map of air flow rate and opening degree of the pressurecontrol valve shown in FIG. 5B, the opening degree of the pressurecontrol valve 27 is set (S36) on the basis of the number of revolutionsof the compressor 22.

After adjusting the opening degree of the pressure control valve 27, thetemperature sensor T1 checks the temperature Te1 of supply air A at theinput of the fuel cell 1 (S37). When the temperature Te1 of supply air Ais detected with the temperature sensor T1, a detection is made as towhether the temperature Te1 is higher than 80° C. (S38). The temperatureTe1 over 80° C. is sufficient for warming up the fuel cell 1. Therefore,if the temperature Te1 is higher than 80° C., the flow control valve 41opens slightly, for example, by 1 deg (S39) such that a part of supplyair A flowing through the bypass passage W2 is fed through the mainpassage W1. Supply air A flowing through the main passage W1 is cooledat the intercooler 23. Furthermore, since the cross-sectional area ofthe main passage W1 is wide, the compression amount of supply air A atthe compressor 22 is decreased. Therefore, the temperature of supply airA flowing to the fuel cell 1 decreases slightly. Meanwhile, if thedetected temperature Te1 in step S37 is equal to or lower than 80° C.,it is determined that the temperature of supply air A is not too high,and supply air A is fed to the fuel cell 1 without varying the openingdegree of the flow control valve 41.

Subsequently, the temperature Te2 of discharged air Ae that isdischarged from the fuel cell 1 is detected with the temperature sensorT2, and a determination is made as to whether the temperature Te2 ishigher than 20° C. (S40). As the result, if the temperature Te2 is equalto or lower than 20° C., the operation returns to step S34 to controlrepeatedly the warm-up of the fuel cell 1. During control of thewarm-up, since the flow control valve 41 gradually and slightlyincreases its opening degree by 1 degree each, it is possible to controlthe temperature of supply air A within a desired temperature range.Furthermore, since supply air A is fed to the fuel cell 1 through themain passage W1 at nd bypass passage W2, flow rate of supply air A doesnot decrease.

Furthermore, if the detected temperature Te2 of discharged air A ishigher than 20° C. in step S40, it is determined that the fuel cell 1has been warmed up, and the flow control valve 41 opens (S41) such thatsupply air A from the compressor 22 flows through the main passage W1.Therefore, the operation shifts to the steady driving and the warm-up iscompleted (S42).

Accordingly, in the first modification, since the opening degree of theflow control valve 41 is adjusted in accordance with a warm-up state ofthe fuel cell 1, supply air A is controlled to a desired temperature atwhich the fuel cell 1 generates electricity effectively. Therefore, evenduring the drive of the fuel cell 1, supply air A having a desiredtemperature will be fed to the fuel cell 1 without decreasing supplyamount of supply air A.

Second Modification

A warm-up apparatus according to a second modification will bedescribed. Parts or elements similar to those previously describedregarding the first embodiment will be denoted by the same referencenumerals and the description thereof will be omitted.

Herein, FIG. 8 is the overall arrangement of a fuel cell systemincluding a warm-up apparatus for the fuel cell according to the secondmodification.

The warm-up apparatus GS3 according to the second modification hassubstantially the same configuration as the warm-up apparatus GS1according to the first embodiment. However, when comparing with thewarm-up apparatus GS1 according to the first embodiment, arrangement ofthe bypass passage W2 differs. Specifically, in the first embodimentshown in FIG. 1, one end of the bypass passage W2 is connected betweenthe passage ON/OFF valve 25 and the humidifier 24. However, in thesecond modification, one end of the bypass passage W2 is connectedbetween the humidifier 24 and the fuel cell 1.

According to the second modification, supply air A flows into the fuelcell via the bypass passage W2 without passing through the intercooler23 and the humidifier 24. When supply air A passes through thehumidifier 24, supply air A is humidified, and at the same time,temperature of supply air A decreases slightly. In the secondmodification, supply air A flowing through the bypass passage W2 doesnot pass through the humidifier 24. As described before in the firstembodiment, supply air A flows through the bypass passage W2 when thefuel cell 1 requires a warm-up. Therefore, in the warm-up apparatus GS3according to the second modification, since supply air A flowing throughthe bypass passage W2 does not pass through the humidifier 24 during thewarm-up of the fuel cell 1, it is possible to complete a warm-up of thefuel cell 1 much more quickly.

Third Modification

A warm-up apparatus according to a third modification will be described.Parts or elements similar to those previously described regarding thefirst embodiment will be denoted by the same reference numerals and thedescription thereof will be omitted.

Herein, FIG. 9 is the overall arrangement of a fuel cell systemincluding a warm-up apparatus for the fuel cell according to the thirdmodification.

The warm-up apparatus GS4 according to the third modification hassubstantially the same configuration as the warm-up apparatus GS1according to the first embodiment. However, according to the warm-upapparatus GS4, as shown in FIG. 9, a passage changeover valve 42 isemployed in place of the passage ON/OFF valve 25 and the check valve 26of the first embodiment shown in FIG. 1. With providing the passagechangeover valve 42, it is possible to decrease the number of requiredparts when compared with the warm-up apparatus GS1 according to thefirst embodiment.

Fourth Modification

A warm-up apparatus according to a fourth modification will bedescribed. Since the configuration of the warm-up apparatus issubstantially the same as the second modification, parts or elementssimilar to those previously described regarding the second modificationwill be denoted by the same reference numerals and the descriptionthereof will be omitted.

Herein, FIG. 10 is the overall arrangement of a fuel cell systemincluding a warm-up apparatus for the fuel cell according to the fourthmodification.

The warm-up apparatus GS according to the fourth modification hassubstantially the same configuration as the warm-up apparatus GS3according to the second modification. However, according to the warm-upapparatus GS5, as shown in FIG. 10, a passage change over valve 42 isemployed in place of the passage ON/OFF valve 25 and the check valve 26of the second modification shown in FIG. 8. With providing the passagechangeover valve 42, it is possible to decrease the number of requiredparts when compared with the warm-up apparatus GS3 according to thesecond modification.

While the invention has been described in detail and with reference tothe first embodiment and modifications thereof, it will be apparent toone skilled in the art that various changes and modifications can bemade therein without departing from the spirit and scope thereof.

For example, the hydrogen supply section is constructed such thathydrogen is fed from the hydrogen tank to the fuel cell. However, rawfuel liquid such as methanol may be used. In this instance, raw fuelliquid is reformed by a reformer to produce hydrogen-enriched fuel gasand then supplied to the fuel cell. Furthermore, the warm-up apparatusof the present invention may be adapted to the hydrogen supply sectionregardless of whether or not discharged hydrogen is circulated. Thehumidifier may be any known type utilizing either a two fluid nozzle orsupersonic wave. Further, the compressor may be a reciprocating type,instead of a turbine rotation type such as a supercharger orturbocharger. Furthermore, as a configuration where a pressure controlvalve is provided between a compressor and a heat exchanger, it ispossible to utilize heat generated by adiabatic compression of thecompressor.

Furthermore, since high-temperature supply air is fed to the fuel cell,a warm-up of the fuel cell is carried out while the fuel cell isgenerating electricity. Therefore, electricity is taken out from thefuel cell shortly after the start up, preventing waste of hydrogen.

Second Embodiment

A warm-up apparatus for a fuel cell according to a second embodiment ofthe invention will be described.

As referential figures relative to the second embodiment, FIG. 11 is theoverall arrangement of a fuel cell system including the warm-upapparatus for the fuel cell according to the second embodiment, and FIG.12 is a schematic explanatory view illustrating the structure of thefuel cell shown in FIG. 11;

As shown in FIG. 11, the fuel cell system FCS comprises a fuel cell 51,an air supply section 52, a hydrogen supply section 53, a controller 54,an anode-cathode heat exchanger (hereinafter referred to as a heatexchanger) 55, etc. The fuel cell system FCS is an electricitygenerating system including a fuel cell 51 as a primary construction.The warm-up apparatus GS (GS6) for the fuel cell 1 substantiallyconsists of the air supply section 52 and the controller 54. The fuelcell system FCS is mounted on an automobile (fuel cell-mounted electricvehicle).

As shown in FIG. 12, the fuel cell 51 is divided into the cathode(oxygen pole) and the anode (hydrogen pole) across an electrolytemembrane 51 c, and each of the poles has an electrode containing aplatinum series catalyst to form a cathode pole 51 b and an anode pole51 d. As an electrolyte membrane 51 c which can be used herein, a solidmacromolecular membrane, such as perfluorocarbon sulfonic acid, which isa proton-exchange membrane, has been known. The electrolyte membrane 51c has a plurality of proton-exchanging groups in the solidmacromolecule, and has a low specific resistance, when being saturatedwith water, lower than 20 Ω-proton at a normal temperature, therebyserving as a proton-conductive electrolyte.

Provided at the outside of the cathode pole 51 b is a cathode-side gaspassage 51 a for feeding supply air A as oxidant gas toward the cathodepole 51 b, and an anode-side gas passage 51 e is provided at the outsideof the anode pole 51 d for feeding supply hydrogen H as fuel gas towardthe anode pole 51 d. The inlet and outlet of the cathode-side gaspassage 51 a are connected to the air supply section 52, and the inletand outlet of the anode-side gas passage 51 e are connected to thehydrogen supply section 53. Although the fuel cell 1 shown in FIG. 12 isillustrated as a single cell for the purpose of simplifying theconfiguration, the fuel cell 51 is actually configured as a laminatestructure having approximately 200 single cells laminated. Since thefuel cell 51 generates heat by the electrochemical reaction whengenerating electricity, a non-shown cooling device is employed forcooling the fuel cell 51.

In the fuel cell 1, supply air A is fed through the cathode-side gaspassage 51 a and supply hydrogen H is fed through the anode-side gaspassage 51 d such that the protons produced at the anode pole 51 d bythe ionization of hydrogen in the presence of the catalyst are migratedin the electrolyte membrane 51 c and reach the cathode pole 51 b. Theprotons reaching to the cathode pole 51 b react with the oxygen ionsproduced from oxygen of the supply air A, thereby producing water. Theproduced water and supply air A containing unused oxygen is dischargedas discharged air Ae from the outlet of the cathode of the fuel cell 51.The discharged air Ae contains a lot of moisture. At the time ofionization of hydrogen, electrons e⁻ are produced in the anode pole 51d. The produced electrons e⁻ reach the cathode pole 51 b via an externalload M such as a motor.

As best seen in FIG. 11, the air supply section 52 comprises an aircompressor 71 as a compressor defined in the claims, a bypass valve 72,an intercooler 73, a restriction valve 74, a cathode humidifier 75, acathode backpressure valve 76, etc. Of these elements, the intercooler73 is arranged in a main passage W3 extending between the bypass valve72 and the cathode backpressure valve 76. The intercooler 73 isfurnished with a radiator 73A which cools cooling water to be circulatedfor cooling the supply air A. The restriction valve 74 is arranged in abypass passage W4 bypassing the intercooler 73. Arranged between theintercooler 73 and the cathode humidifier 75 is the heat exchanger 55.With this configuration, supply gas flowing through the bypass passageW4 does not flow to the intercooler 73. The cross-sectional area of thebypass passage W4 is smaller than that of the main passage W3.Therefore, pressure of supply air A at the discharge side of the aircompressor 71 becomes higher when flowing through the bypass passage W4than when flowing through the main passage W3. As a result, temperatureof supply air A rises higher. Preferably, the cross-sectional area ofthe bypass passage W4 is set ½ or less of that of the main passage W3.The air supply section 52 is provided with temperature sensors T4 to T7for detecting temperatures of supply air A, cooling water supplied tothe intercooler 73, and the like.

The air compressor 71 is mainly consists of a supercharger (not shown)and a motor (not shown) for driving the supercharger. Supply air Apasses through a non-shown air cleaner for removal of impurities orcontaminants contained in the air, and flows into the air compressor 71.The air compressor 71 applies adiabatic compression to supply air A thatis used in the fuel cell as oxidant gas, and feeds the compressed airunder pressure toward the fuel cell 1. During adiabatic compression,supply air A is heated. The heated supply air A contributes towarming-up of the fuel cell 1.

The bypass valve 72 consists of a passage switching valve, and switchesa flow of supply air A between the main passage W3 and the bypasspassage W4 on the basis of a changeover signal outputted from thecontroller 54.

The intercooler 73 is furnished with a cooling water channel, throughwhich cooling water flows. During the normal driving of the fuel cell51, the intercooler 73 cools supply air A from the air compressor 71 byheat exchange between cooling water and supply air A. The radiator 73Ais connected to the intercooler 73. The radiator 73A cools coolingwater, the temperature of which rises due to heat caused upon coolingsupply air A at the intercooler 73, for example, with a cooling fan. Thetemperature of supply air A that is fed from the air compressor 71during the normal driving of the fuel cell 51 is usually about 120° C.However, the fuel cell 51 is driven in the temperature range of about 80to 90° C. For this reason, supply air A is cooled down to a temperatureof about 60 to 75° C., and then introduced into the fuel cell 51.

The restriction valve 74 is an opening degree adjustable valve, whichadjusts the opening degree thereof. Adjusting the opening degree of therestriction valve 74 allows the bypass passage W4 through which supplyair A flows to decrease a part of its diameter.

The cathode humidifier 75 is a fuel cell discharged gas supplying type,and substantially consists of a housing and a bundle of hollow fibermembranes made by a number of, for example, 5000 hollow fiber membranesbound together and accommodated in the housing. Supply air A flowswithin the hollow fiber membranes, and discharged air Ae flows outsidethe hollow fiber membranes within the housing. Since water is producedin the fuel cell 51 upon generation of electricity and discharged air Aecontains a lot of water or moisture, supply air A is humidified bymoisture exchanging with the water. As the cathode humidifier 75, anyknown device may be used other than this fuel cell discharged gassupplying type. For example, one known humidifier (a kind of carburetor)comprises a venturi, a water tank, a siphon tube connecting the venturiand the water tank, etc, and supply air A is humidified by water, whichis stored in the water tank for the purpose of humidifying air A and isdrawn by Venturi effect for spraying the same.

The cathode backpressure valve 76 consists of a butterfly valve (notshown) and a stepping motor (not shown) for driving the butterfly valve,etc. The cathode backpressure valve 76 controls pressure (dischargepressure) of discharged air Ae that is discharged from the fuel cell 51by decreasing or increasing the opening degree of the cathodebackpressure valve 76. Decreasing the opening degree of the cathodebackpressure valve 76 allows the fuel cell 51 to increase its dischargepressure, and therefore, the temperature rising range of discharged airAe increases proportionally to the increasing discharge pressure.Meanwhile, increasing the opening degree of the cathode backpressurevalve 76 allows the fuel cell 51 to decrease its discharge pressure, andtherefore, the temperature rising range of discharged air Ae decreasesproportionally to the decreasing discharged pressure.

Each of the temperature sensors T4 to T7 comprises a thermistor and thelike. Of these temperature sensors, the temperature sensor T4 detectstemperature of supply air A at the inlet of the cathode of the fuel cell51, the temperature sensor T5 detects temperature of discharged air Aeat the outlet of the cathode of the fuel cell 51, the temperature sensorT6 detects temperature of cooling water that is supplied from theradiator 73A to the intercooler 73, and the temperature sensor T7detects temperature of supply air A that is fed to the heat exchanger55. Each temperature sensor T4 to T7 transmits a detection signal to thecontroller 54. A warm-up state of the fuel cell 51 is determined basedon the temperature Te5 of discharged air Ae detected with thetemperature sensor T5. Furthermore, ambient temperature is determinedbased on the temperature Te6 of cooling water detected at theintercooler 73 with the temperature sensor T6.

As shown in FIG. 11, the hydrogen supply section 53 comprises an anodesupply device 81, an anode circulation device 82, an anode humidifier83, etc.

The anode supply device 81 comprises, for example, a hydrogen gascylinder and a regulator. The hydrogen gas cylinder consists of anon-shown high-pressure hydrogen bomb, and stores supply hydrogen H tobe introduced to the anode of the fuel cell 51. Stored supply hydrogen His pure hydrogen, and the pressure thereof ranges from 15 to 20 MpaG(150-200 kg/cm²G). The hydrogen gas cylinder may be made from hydrogenabsorbing alloys, and may store hydrogen at a pressure of about 1 MPaG(10 kg/cm²G). The regulator comprises a diaphragm (not shown), apressure regulating spring (not shown) and the like. The regulator is apressure control valve for decreasing pressure of supply hydrogen H thatis stored at a high pressure to a predetermined pressure so as to enablethe use of supply hydrogen H under a certain constant pressure.

The anode circulation device 82 consists of, for example, a hydrogencirculating pump. This hydrogen circulating pump consists of a non-shownejector and the like. The hydrogen circulating pump utilizes a flow ofsupply hydrogen H flowing toward the anode of the fuel cell 51 so as toabsorb spent supply hydrogen H after the use in the fuel cell 51 as fuelgas, viz. discharged hydrogen He discharged from the anode of the fuelcell 51, and circulates the spent supply hydrogen H. The reason forcirculating and utilizing discharged hydrogen He is that supply hydrogenH stored in the hydrogen gas cylinder of the anode supply device 81 ispure hydrogen.

The controller 54 comprises a CPU, a memory, an input/output interface,an A/D converter, a bus, etc. The controller entirely and systematicallycontrols the fuel cell system FCS as well as controls temperature ofsupply air A to be fed to the fuel cell 51. As mentioned above, thecontroller 54 receives detection signals from the temperature sensors T4to T7. The controller 54 also transmits control signals with respect tothe air compressor 71, the bypass valve 72, the restriction valve 74,and the cathode backpressure valve 76. In this second embodiment, thecontroller 54 switches the bypass valve 72, and adjusts the openingdegree of the restriction valve 74, so that a flow of supply air A fromthe air compressor 71 is switched between the main passage W3 and thebypass passage W4. When supply air A flows through the bypass passageW4, the opening degree of the restriction valve 74 is adjusted to adjusttemperature of supply air A. Therefore, the bypass valve 72 and therestriction valve 74 form a heat quantity adjustment device defined inthe claims.

The heat exchanger 55 is arranged between an air passage and a hydrogenpassage. The air passage extends from the air compressor 71 to thecathode of the fuel cell 51, and the hydrogen passage extends from theanode supply device 81 to the anode of the fuel cell 51. The heatexchanger 55 comprises an air flow passage for feeding supply air A anda hydrogen flow passage for feeding supply hydrogen H, and heat ofsupply air A flowing through the air flow passage is transmitted tosupply hydrogen H flowing through the hydrogen flow passage.

With reference to FIG. 13, one operation example at start up of thewarm-up apparatus GS6 according to the second embodiment will bedescribed (see also FIG. 11 when necessary).

Herein, FIG. 13 is a flow chart partly showing a series of control flowsof the warm-up apparatus according to the second embodiment. The targettemperature of supply air A to be fed to the fuel cell 51 is in therange of between 65° C. and 80° C.

In order to start up the fuel cell, when the ignition switch is ON(S51), the air compressor 71 is actuated (S52). Upon actuating the aircompressor 71, the temperature of supply air A at the inlet of the fuelcell 51 and the temperature of discharged air Ae at the outlet of thefuel cell 51 are detected with the temperature sensors T4, T5 (S53).Subsequently, a determination is made as to whether the temperature Te5of discharged air Ae detected with the temperature sensor T5 is higherthan 15° C., and at the same time, a determination is made as to whetherthe temperature Te5 of discharged air Ae is higher than the temperatureTe4 of supply air A. If the temperature Te5 of discharged air Ae ishigher than 15° C., it is determined that the fuel cell 51 has beenwarmed up and the fuel cell 51 does not require a warm-up. Meanwhile, ifthe temperature Te5 is higher than the temperature Te4 of supply air A,it is also determined that the fuel cell 51 has been warmed up and thefuel cell 51 does not require a warm-up. Therefore, when either one ofthe above conditions is satisfied, i.e. the temperature Te5 is higherthan 15° C. or the temperature Te5 is higher than the temperature Te4,it is determined that the fuel cell 51 does not require a warm-up. Inthis event, idling drive of the fuel cell 51 is started (S55) whilecontinuously driving the air compressor 71. These operations are carriedout just after turning on the ignition switch.

Meanwhile, in step S54, if the detected temperature Te5 of dischargedair Ae is equal to or lower than 15° C. and the detected temperature Te5of discharged air Ae is equal to or lower than the temperature Te4 ofsupply air A, the temperature of cooling water at the intercooler 73 isdetected with the temperature sensor T6 (S56). Now, the temperature ofcooling water is considered as being substantially equal to thetemperature of ambient air. However, if the temperature of cooling wateris higher than 15° C., it is determined that a warm-up of the fuel cell51 is unnecessary. For this reason, a determination is made as towhether the temperature Te6 of cooling water is higher than 15° C.(S57). As the result, if the temperature Te6 is higher than 15° C., itis determined that the fuel cell 51 does not require a warm-up. Andidling drive of the fuel cell 51 is started (S55) while continuouslydriving the air compressor 71. Meanwhile, in step S57, if the detectedtemperature Te6 is equal to or lower than 15° C., the bypass valve 72switches to ON (S58) to proceed into a low-temperature start up mode(S59), so that supply air A from the air compressor 71 is fed throughthe bypass passage W4. A flow of supply air A is switched between themain passage W3 and the bypass passage W4, and supply air A flowsthrough the bypass passage W4 when the bypass valve 72 is ON, and supplyair A flows through the main passage W3 when the bypass valve 72 is OFF.When supply air A flows through the bypass passage W4, supply air Abypasses the intercooler 73 and flows into the fuel cell 51. Sincesupply air A bypassing the intercooler 73 is not cooled by theintercooler 73, air warmed at the air compressor 71 is directly fed tothe fuel cell 51.

Herein, supply air A that is fed to the fuel cell 51 passes through theheat exchanger 55. Also, supply hydrogen H that is fed to the anode ofthe fuel cell 51 flows through the heat exchanger 55. Now, thetemperature of supply hydrogen H is substantially equal to thetemperature of supply air A prior to being warmed up by the aircompressor 71, and is lower than the temperature of supply air A afterbeing warmed up. Usually, the flow rate of supply hydrogen H isextremely low when compared with the flow rate of supply air A. Sinceboth supply air A and supply hydrogen H pass through the heat exchanger55, heat of supply air A is transmitted to supply hydrogen H, so thatsupply hydrogen H is warmed up to a temperature substantially equal tothe supply air A. For this reason, supply air A is required to have aheat quantity sufficient to warm up supply hydrogen H, and therefore,supply air A is warmed up to a temperature higher than 65 to 80° C., ofwhich temperature supply air A is fed to the fuel cell 51.

Accordingly, supply air A is fed to the cathode of the fuel cell 51 andsupply hydrogen H is fed to the anode of the fuel cell 51 while the aircompressor 71 warms up supply air A and supply hydrogen H is warmed upwith heat of supply air A. This enables warming-up of the devices notonly in the cathode system but also in the anode system. Also, thisenables warming-up for both the cathode and the anode to thereby warm upthe whole fuel cell 51 uniformly and quickly. Therefore, it is possibleto decrease time required for warming up the fuel cell 51 to perform adesired electricity generation capacity. The fuel cell 51 is thereforewarmed up quickly. In the low-temperature start up mode, the aircompressor 71 is driven with an electric power (e.g. 5 kW) greater thanrequired during the normal idling (e.g. 500 W) so as to increase heatingamount of supply air A due to adiabatic compression of the aircompressor 71. Furthermore, opening degree of the restriction valve 74is each time determined based on, for example, temperature of supply airA just before being fed to the fuel cell 51 and detected with thetemperature sensor T4.

During the low-temperature start up mode, the temperature Te4 of supplyair A just before flowing into the fuel cell 51 is detected with thetemperature sensor T4, and the temperature Te5 of discharged air Aedischarged from the fuel cell 51 is detected with the temperature sensorT5 (S60). And the supply air elevated temperature ΔTe4 compared with theprevious temperature of supply air A that was fed to the fuel cell 51last time is calculated, and the discharged air elevated temperatureΔTe5 compared with the previous temperature of discharged air Ae thatwas discharged from the fuel cell 51 last time is calculated.Subsequently, a determination is made as to whether each of the supplyair elevated temperature ΔTe4 and the discharged air elevatedtemperature ΔTe5 is higher than 0° C. (S61). If either one of the supplyair elevated temperature ΔTe4 and the discharged air elevatedtemperature ΔTe5 is equal to or lower than 0° C., the operation returnsto step S59 to carry out continuously the low-temperature start up mode.

Meanwhile, when both the supply air elevated temperature ΔTe4 and thedischarged air elevated temperature ΔTe5 are higher than 0° C., thetemperature Te6 of cooling water at the intercooler 73 is then detectedwith the temperature sensor T6 (S62). And a determination is made as towhether the temperature Te6 is lower than 15° C. (S63). As the result,if the temperature Te6 is lower than 15° C., supply air A is not fed tothe intercooler 73 to prevent supply air A from being too cooled due tothe intercooler 73 that is not warmed up yet. For this reason, after thelow-temperature start up mode is cleared (S64), the restriction of therestriction valve 74 is wholly open (S65) to make supply air A bypassthe intercooler 73, and all supply air A is fed through the bypasspassage W4. And idling drive of the fuel cell 51 is started (S66) whilecontinuously driving the air compressor 71. In this event, the aircompressor 71 is driven, for example, by electric power of 500 W.

Subsequently, the temperature Te6 of cooling water at the intercooler 73is detected with the temperature sensor T6 (S67), and a determination ismade as to whether the temperature Te6 is lower than 15° C. (S68). Ifthe temperature Te6 is less than 15° C., the operation returns to stepS66 to carry out continuously the idling drive of the fuel cell 51. Sucha feedback control is repeated and the same operation is carried outuntil the temperature Te6 of cooling water is equal to or greater than15° C. On the contrary, if the temperature Te6 is equal to or greaterthan 15° C., it is determined that the intercooler 73 is ready, and theoperation proceeds to step S69 shown in FIG. 15.

Meanwhile, in step S63, if the detected temperature Te6 of cooling waterat the intercooler 73 is equal to or greater than 15° C., it isdetermined that the intercooler 73 is not cool, and the operationproceeds to step S69.

In step S69, a determination is made as to whether or not the fuel cell51 is in the low-temperature start up mode. As the result of thedetermination, if not in the low-temperature start up mode, theoperation skips step S70 and then proceeds to step S71. However, if thelow-temperature start up mode is determined in step S69, thelow-temperature start up mode is cleared (S70). When the low-temperaturestart up mode is cleared, the bypass valve 72 is switched to OFF (S71)so that supply air A from the air compressor 71 flows through the mainpassage W3. Supply air A flowing through the main passage W3 is adjustedto a predetermined temperature at the intercooler 73 and then fed to thefuel cell 51. And idling drive of the fuel cell 51 is carried out (S72)while continuously driving the air compressor 71. The warm-up of thefuel cell 51 is then completed (S73).

As mentioned above, according to the second embodiment, supply air Athat is warmed by the air compressor 71 and fed to the cathode of thefuel cell 51 as well as supply hydrogen H that is fed to the anode ofthe fuel cell 51 are respectively flown through the heat exchanger 55.At the heat exchanger 55, heat of supply air A is transmitted to supplyhydrogen so that the supply hydrogen H is warmed up. Accordingly, supplyhydrogen H passing through the heat exchanger 55 enables a warm-up ofthe anode circulation device 82 and the anode humidifier 83.Furthermore, it is possible to warm up directly the anode of the fuelcell 51 without transmitting heat through the cathode of the fuel cell51. Therefore, it is possible to warm up the whole fuel cell 51 quickly.

Upon determining completion of the warm-up of the fuel cell 51, inaddition to the temperature of discharged air Ae discharged from thefuel cell 51, the temperature of ambient air may be measured with anon-shown temperature sensor, for example, provided at the inlet of theair compressor 71, and the bypass valve 72 may be controlled based onthe temperature of ambient air. When ambient air is low in temperature,in order to increase the temperature of supply air A to a desiredtemperature with respect to the fuel cell 51, it is necessary toincrease heat quantity that is given to supply air A. For this reason,when the temperature of ambient air is low, a control is made such thatflow rate of supply air A flowing through the bypass passage W4increases. On the contrary, when the temperature of ambient air is high,a control is made such that flow rate of supply air A flowing throughthe main passage W3 increases. Therefore, the temperature of supply airA is adjusted to a desired temperature.

A warm-up operation during the normal driving will be described. Sincethe warm-up operation in the normal driving is carried out by thewarm-up apparatus GS6 illustrated in FIG. 11, a reference is also madeto FIG. 11 when necessary.

FIG. 16A is a flow chart showing a warm-up operation in the normal mode.

As shown in FIG. 16A, when the fuel cell 51 is in the normal mode (S80),the temperature Te7 of supply air A that is fed to the heat exchanger 55is detected with the temperature sensor T7, and a determination is madeas to whether the temperature Te7 is lower than 60° C. (S81). When thefuel cell 51 is in the normal mode, the bypass valve 72 is OFF to coolsupply air A by means of the intercooler 73, so that supply air A flowsthrough the main passage W3. Herein, if the temperature Te7 is lowerthan 60° C., it is impossible to supply the fuel cell 51 with supply airA in the optimum temperature range of between 65° C. and 80° C.Meanwhile, in step S81, if the temperature Te7 is equal to or higherthan 60° C., supply air A having a temperature within the optimumtemperature range will be fed to the fuel cell 51. Therefore, the bypassvalve 72 remains OFF (S82), and the operation is completed while supplyair A is flowing through the main passage W3.

If the temperature Te7 of supply air A detected with the temperaturesensor T7 is lower than 60° C., since the fuel cell 51 requires warmsupply air A, the bypass valve 72 is switched to ON (S83) to feed supplyair A through the bypass passage W4. Since supply air A flowing throughthe bypass passage W4 is fed to the fuel cell 51 bypassing theintercooler 73, warm supply air is fed to the fuel cell 51. Furthermore,upon feeding supply air A through the bypass passage W4, pressure of theair compressor 71 at the outlet is adjusted by the restriction valve 74arranged in the bypass passage W4. In this event, opening degree of therestriction valve 74 is determined from a function f(Te7) (S84), inwhich the temperature Te7 of supply air A just before flowing into theinlet of the heat exchanger 55 is considered as a parameter. Thefunction utilized for this purpose is shown in FIG. 16B. As shown inFIG. 16B, in the region where supply air A just before flowing into theheat exchanger 55 has a temperature Te7 lower than 60° C., the openingdegree of the restriction valve 74 becomes smaller as the temperatureTe7 of the supply air A becomes lower. The smaller the opening degree ofthe restriction valve 74, the higher the pressure of supply air A at theoutlet of the air compressor 71, which leads to increasing temperatureof supply air A. Therefore, it is possible to raise the temperature ofsupply air A that is fed to the fuel cell 51.

The opening degree of the restriction valve 74 becomes greater as thetemperature Te7 increases to 60° C. The greater the opening degree ofthe restriction valve 74, the smaller the pressure of supply air A atthe outlet of the air compressor 71, which leads to decreasedtemperature rising range of supply air A. Therefore, it is possible tocontrol supply air A to a desired temperature for supplying to the fuelcell 51.

After carrying out the aforementioned control, the warm-up operation ofthe fuel cell 51 in the normal mode is completed (S85). Accordingly, awarm-up of the fuel cell 51 is carried out during the normal driving ofthe fuel cell 51.

Modification of Second Embodiment

A modification of the second embodiment will be described. Parts orelements similar to those previously described regarding the secondembodiment will be denoted by the same reference numerals anddescription thereof will be omitted.

Herein, FIG. 17 is the overall arrangement of a fuel cell systemincluding a warm-up apparatus for the fuel cell according to amodification of the second embodiment.

As shown in FIG. 17, the warm-up apparatus GS7 for the fuel cell hassubstantially the same configuration as the warm-up apparatus GS6according to the second embodiment shown in FIG. 11. However, accordingto the warm-up apparatus GS7, as shown in FIG. 17, a first and secondcommon piping 91, 92 are employed in placed of the heat exchanger 55 inthe second embodiment shown in FIG. 11. In this modification, thesecommon piping 91, 92 functions as a heat exchanger where heat of supplyair is transmitted to supply hydrogen.

Likewise the second embodiment, switching between the main passage W3and the bypass passage W4 is carried out with the bypass valve 72. Also,likewise the second embodiment, adjusting the opening degree of therestriction valve 74 provided in the bypass passage W4 enables to varythe cross-sectional area of the bypass passage W4 and hence to adjustpressure of the air compressor 71 at the outlet, thereby adjustingtemperature of supply air A.

In this modification, supply air A from the air compressor 71 isintroduced into the fist common piping 91 via the intercooler 73. Supplyair A flowing out from the first common piping 91 is introduced throughthe cathode humidifier 75 and into the second common piping 92. Supplyair A flowing out from the second common piping 92 is fed to the cathodeof the fuel cell 51. Discharged air Ae discharged from the cathode ofthe fuel cell 51 flows along the same flow passage as the secondembodiment.

Meanwhile, supply hydrogen H from the anode supply device 81 isintroduced through the anode circulation device 82 into the first commonpiping 91. The cross-section of the first common piping 91 is shown inFIG. 18. As shown in FIG. 18, the first common piping 91 has a doublepiping structure, in which supply hydrogen flows through a hydrogen flowpassage HF formed within the inner tube 91A. Formed between the outersurface of the inner tube 91A and the inner surface of the outer tube91B is an air flow passage AF, through which supply air flows. The firstcommon piping 91 has a simple double piping structure, and supply airand supply hydrogen flow parallelly in the same flow direction withinthe air flow passage AF and the hydrogen flow passage HF, so that heatof supply air A is transmitted to supply hydrogen H. According to thismodification, supply air A and supply hydrogen flow parallelly in thesame direction. However, of course, supply air A and supply hydrogen mayflow in the counter direction.

Supply hydrogen H flowing out from the first common piping 91 isintroduced through the anode humidifier 83 into the second common piping92. As shown in FIG. 18, likewise the first common piping 91, the secondcommon piping 92 includes an inner tube 92A and an outer tube 92B. Ahydrogen flow passage HF is formed within the inner tube 92A for feedingsupply hydrogen H, and an air flow passage AF is formed between theouter surface of the inner tube 92A and the inner surface of the outertube 92B for feeding supply air. With such a constitution, heat istransmitted from supply air to supply hydrogen while supply air andsupply hydrogen flow through the respective flow passages.

Supply air flowing out from the second common piping 92 is fed to theanode of the fuel cell 51. Discharged hydrogen He discharged from theanode of the fuel cell 51 is introduced into the anode circulationdevice 82 for recycling.

Likewise the second embodiment, the warm-up apparatus GS7 according tothis modification controls the bypass valve 72 and the restriction valve74 on the basis of each temperature signal outputted from thetemperature sensors T4 to T7. For this reason, likewise the secondembodiment, by supplying the fuel cell 51 with supply air A and supplyhydrogen H each having an appropriate temperature, not only devices inthe cathode system but also devices in the anode system are warmed up,and the cathode and the anode of the fuel cell 51 are quickly warmed up,thereby completing warming-up of the whole fuel cell 51 quickly withoutrequiring a dedicated electric heater or hydrogen-combustion heater.

Furthermore, according to this modification, since heat of supply air Ais transmitted to supply hydrogen H with the use of the common piping91, 92, it is possible to reduce the size of the whole apparatus whencompared with the second embodiment utilizing the heat exchanger 55.

While the invention has been described in detail and with reference tothe second embodiment and modification thereof, it will be apparent toone skilled in the art that various changes and modifications can bemade therein without departing from the spirit and scope thereof.

For example, in the aforementioned examples, control of the bypass valveand restriction valve is carried out on the basis of the temperature ofsupply air flowing to the fuel cell 51 and the temperature of coolingwater at the cooler of the intercooler. Meanwhile, a condition of thefuel cell is detected based on the amount of electricity generationgenerated at the fuel cell, and by this condition, temperatures ofsupply air and supply hydrogen that are fed to the fuel cell may becontrolled. To be more specific, for example, amount of hydrogenconsumption increases as amount of electricity generation of the fuelcell increases, and the amount of supply hydrogen to the fuel cellincreases as well. Therefore, in order to provide such a lot of hydrogenwith heat, heat quantity of air is increased by way of increasing flowrate of air that flows through the bypass passage. On the contrary, ifthe amount of electricity generation generated at the fuel cell issmall, the amount of hydrogen consumption is small, and thus, a fewamount of hydrogen requires heat. Therefore, since air requires a smallamount of heat, the amount of air flowing through the main passage isincreased. Accordingly, it is possible to feed air and hydrogen eachhaving a desired temperature to the fuel cell. The amount of electricitygeneration generated at the fuel cell is detected, for example, with anon-shown ECU.

Furthermore, in the aforementioned examples, a bypass valve is used as aheat quantity adjustment device for switching between the main passageand the bypass passage. However, for example, a flow control valve maybe employed for adjusting the amount of air flowing through the mainpassage and bypass passage.

Moreover, the hydrogen supply section is constructed such that hydrogenis fed from the hydrogen tank to the fuel cell. However, raw fuel liquidsuch as methanol may be used. In this instance, raw fuel liquid isreformed by a reformer to produce hydrogen-enriched fuel gas and thensupplied to the fuel cell.

1. A warm-up apparatus for a fuel cell comprising: a compressor forfeeding supply gas to the fuel cell, the supply gas being compressed sothat a temperature of the supply gas is elevated; a main passageconnecting the compressor and the fuel cell and feeding the supply gas;an intercooler arranged in the main passage and cooling the supply gas;a humidifier arranged in the main passage and humidifying the supplygas; a bypass passage feeding the supply gas from the compressor to thefuel cell at a warming-up of the fuel cell while bypassing theintercooler and the humidifier, a cross-sectional area of the bypasspassage being smaller than that of the main passage; and a controller isprogrammed to control the number of revolutions of the compressor;wherein, if a warm-up of the fuel cell is required and the supply gasflows through the bypass passage, the controller controls the compressorby setting the number of revolutions of the compressor to apredetermined value corresponding to a temperature of the fuel cell,with reference to a predetermined map in which the number of therevolutions of the compressor is set to be increased as the temperatureof the fuel cell decreases, to feed the supply gas to the fuel cell, ifa temperature of the supply gas fed to the fuel cell gets to an upperlimit of a predetermined temperature for the supply gas fed to the fuelcell and exceeds a temperature sufficient for warming-up which issufficient for warming-up the fuel cell, the controller controls thecompressor by decreasing the number of revolutions of the compressorfrom the predetermined value so that the temperature of the supply gasdoes not exceed the temperature sufficient for warming-up, when thecontroller controls the compressor by the predetermined value of therevolution number, and the intercooler is arranged downstream of thecompressor and the supply gas is air.
 2. A warm-up apparatus for a fuelcell according to claim 1, wherein the supply gas is fed either to themain passage or the bypass passage in accordance with a warming-up stateof the fuel cell.
 3. A warm-up apparatus for a fuel cell according toclaim 1, wherein the supply gas is fed either to the main passage or thebypass passage in accordance with a warming-up state of the fuel cell.4. A warm-up apparatus for a fuel cell according to claim 1, wherein aflow rate adjustment device is provided for adjusting a ratio of flowrates of the supply gas, which passes through the main passage and thebypass passage.
 5. A warm-up apparatus for a fuel cell according toclaim 4, wherein a flow rate of the supply gas flowing through thebypass passage is adjusted in accordance with a warming-up state of thefuel cell.
 6. A warm-up apparatus for a fuel cell according to claim 1,wherein the number of revolutions of the compressor is controlled inaccordance with a warming-up state of the fuel cell.
 7. A warm-upapparatus for a fuel cell according to claim 2, wherein the number ofrevolutions of the compressor is controlled in accordance with awarming-up state of the fuel cell.
 8. A warm-up apparatus for a fuelcell according to claim 4, wherein the number of revolutions of thecompressor is controlled in accordance with a warming-up state of thefuel cell.
 9. A warm-up apparatus for a fuel cell according to claim 5,wherein the number of revolutions of the compressor is controlled inaccordance with a warming-up state of the fuel cell.